Footwear, particularly athletic footwear, is worn in a variety of activities including running, walking, hiking, other team and individual sports, and any activity where the protection and support of human feet is desired. In one configuration, an article of footwear includes a sole and an upper that form a cavity in which a user places his or her foot. The sole of the footwear engages the bottom of the foot and separates the foot from the ground. The sole often consists of one or more layers of materials including leather, rubber, foam, and plastics that provide shock absorption and support to the foot. The upper extends outwardly from an outer peripheral edge of the sole and covers at least a portion of the foot to hold the footwear in place. Uppers in athletic shoes are usually formed from one or more pieces of fabric, leather, and/or plastic that are stitched or otherwise attached together. Various fasteners including shoelaces and hook and loop fasteners are used to secure the foot in place within the footwear.
In an article of footwear, the sole provides cushioning and support for the foot and helps to maintain traction between the foot and the ground while running or walking. The sole deforms as the shape of the foot changes during each stride, and then returns to an undeformed configuration as the foot leaves the ground.
Proper engagement between the foot and the upper and sole of the shoe can improve the comfort and protection that the shoe provides to a wearer. The human foot has various sections including the forefoot, midfoot, and heel. During walking or running, the human foot transfers energy into the ground through the sole. Some mechanical energy is also stored in the sole as the sole deforms during a stride, and the mechanical energy is released as the foot and the sole leave the ground. Thus, improvements to footwear that enable each section of the foot to engage the footwear comfortably and improvements that reduce the effort needed to walk or run while wearing the footwear would be beneficial.